docs: Added documentation for LLMProviders and named instances

web/docs/src/content/docs/architecture/llm-providers.md

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+---
+title: LLM Providers & Configuration
+description: Details of the LLM provider instances, task routing, and self-bootstrapping setup in Omnia.
+sidebar:
+  order: 5
+---
+
+In Omnia, all non-player character behaviors, action validation, intent decoding, and time step logic are simulated using Large Language Models (LLMs). The LLM subsystem is built around **polymorphism, key instance management, and task provider routing**.
+
+## Core Interfaces
+
+All LLM providers implement the common `ILLMProvider` interface defined in `packages/llm/src/llm.ts`:
+
+```typescript
+export interface ILLMProvider {
+  providerName: string;
+  generateStructuredResponse<T extends z.ZodTypeAny>(
+    request: LLMRequest<T>,
+  ): Promise<LLMResponse<z.infer<T>>>;
+  lastCalls?: LLMCallRecord[];
+}
+```
+
+The codebase provides two primary implementations:
+1. **`GeminiProvider`:** The production provider utilizing Google's Gemini Models via the `@langchain/google-genai` SDK.
+2. **`MockLLMProvider`:** A stateless, pre-programmed mock provider used for fast, deterministic unit testing and local integration tests.
+
+---
+
+## LLM Provider Instances
+
+To support multiple different API keys, key rotation, and model variation, Omnia utilizes a **Provider Instance model** rather than relying on static configuration:
+
+```typescript
+export interface LLMProviderInstance {
+  id: string;
+  name: string;
+  providerName: string;
+  apiKey: string;
+  isActive: boolean;
+  modelName?: string;
+}
+```
+
+Users can register multiple provider instances in the **Configuration Page** under the GUI. Each instance is given:
+* A friendly, human-readable name (e.g., `"Gemini Production Key"`, `"Experimental Gemini Pro"`).
+* A provider type (e.g., `google-genai`, `mock`).
+* An API key credential.
+* A custom target model name (e.g., `gemini-2.5-flash` or `gemini-2.5-pro`).
+* An **Active** status flag (one key is marked as globally active).
+
+Configurations are stored globally in `data/settings.db` (separated from specific simulation run databases like `data/sim-*.db` to keep key storage and audit logs isolated).
+
+---
+
+## Task Provider Routing
+
+During a simulation run, the engine executes four distinct LLM operations. To optimize costs, latency, or model accuracy, you can route each of these tasks to different LLM provider instances:
+
+| Task Name | Key ID | Description | Default Model |
+| :--- | :--- | :--- | :--- |
+| **Actor Prose Generation** | `actor-prose` | Generates roleplay and narrative behavioral prose for Non-Player Characters. | `gemini-2.5-flash` |
+| **LLM Validator** | `llm-validator` | Arbitrates and validates proposed actions against the world state rules and constraints. | `gemini-2.5-flash` |
+| **Intent Decoder** | `intent-decoder` | Parses and splits free-text actions/prose into structured intent sequences. | `gemini-2.5-flash` |
+| **TimeDelta Generator** | `timedelta` | Calculates the duration of character actions to advance the game clock. | `gemini-2.5-flash` |
+
+If no specific provider instance is mapped to a task, the task automatically routes to the globally marked **Active** provider instance.
+
+---
+
+## Automatic Bootstrapping (Environment Key Fallback)
+
+To maintain backwards-compatibility and support headless runs, live evaluation suites, and automated unit tests without requiring database pre-configuration, the config manager supports **self-bootstrapping**:
+
+1. When the provider manager queries the active key instance, if `data/settings.db` contains **0 registered keys**, it checks the process environment for `GOOGLE_API_KEY`.
+2. If `process.env.GOOGLE_API_KEY` is present, it automatically creates, saves, and activates a default provider instance (`Default (Env)`) in `settings.db`.
+3. If database write locks occur (e.g., during high-concurrency Vitest test suites), the system seamlessly returns a temporary in-memory `LLMProviderInstance` to keep execution fluent and error-free.
+
+---
+
+## Developer Guide: Managing Mappings
+
+Configuration settings are managed through `ProviderManager` static methods:
+
+```typescript
+// Query the active provider configuration
+const activeConfig = ProviderManager.getActive();
+
+// List all registered provider instances
+const allConfigs = ProviderManager.list();
+
+// Retrieve task-specific mappings
+const mappings = ProviderManager.getMappings(); // e.g., { "actor-prose": "provider-123" }
+
+// Map a task to a provider instance
+ProviderManager.setMapping("actor-prose", "provider-123");
+```